Fasting

Restricting the amount of calories we consume, while avoiding malnutrition, may extend lives and reduce the risk of chronic disease, suggest results from a monkey study.

Findings published in Science indicate that 80 per cent of rhesus monkeys who consumed a calorie restricted diet without being malnourished were still alive after 20 years, compared to only 50 per cent of control animals who ate freely.

"We have been able to show that caloric restriction can slow the aging process in a primate species," said study leader Professor Richard Weindruch from the University of Wisconsin-Madison. "We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival."

Not surprisingly, longevity and enhanced quality of life is the ultimate aim of most research into diet and nutrition, but very few studies actually achieve such a link. The trick now will be to see if it can be carried over to humans - something the researchers say is highly unlikely due to the extremely restrictive nature of such a diet.

“Our data indicate that adult-onset moderate caloric restriction delays the onset of age-associated pathologies and promotes survival in a primate species,” wrote the researchers.

“Given the obvious parallels between rhesus monkeys and humans, the beneficial effects of caloric restriction may also occur in humans. This prediction is supported by studies of people on long-term caloric restriction, who show fewer signs of cardiovascular aging,” they added.

“The effect of controlled long-term caloric restriction on maximal life span in humans may never be known, but our extended study will eventually provide such data on rhesus monkeys.”

Study Details

The Wisconsin-based researchers started their study in 1989 with 30 rhesus macaques (Macaca mulatta), and subsequently expanded this to 76. The animals were divided into two groups; one was allowed to eat freely (control group), while the other group had their energy intake restricted by 30 per cent.

According to Weindruch and his co-workers, macaques typically live for about 27 years in captivity. All the monkeys were aged between 7 and 14 when introduced into the study, they added.

In addition to increased lifespan in the calorie restriction group, a halving of the incidence of cancer and cardiovascular disease was observed in this group, compared to the control animals.

Furthermore, while free eating resulted in diabetes or impaired glucose regulation no animal on the restricted diet developed these conditions. "So far, we've seen the complete prevention of diabetes," said Weindruch.

Brain Boosting

Brain health was also better in the animals with restricted calorie diets, said the researchers, particularly the parts of the brain responsible for motor control and executive functions such as working memory and problem solving.

"It seems to preserve the volume of the brain in some regions. It's not a global effect, but the findings are helping us understand if this dietary treatment is having any effect on the loss of neurons," said co-researcher Sterling Johnson.

"The atrophy or loss of brain mass known to occur with aging is significantly attenuated in several regions of the brain. That's a completely new observation," added Weindruch.

Results of Scientific Research Into Fasting - - National Institute of Aging & National Academy of Sciences - April 2003

Periodic fasting may be just as good for the health as cutting back sharply on calories, even if overall food intake is not reduced by the fasts. United States researchers who made the finding are planning to see if what works in mice is also good for people. Several recent studies have reported a range of benefits from a sharply restricted diet, including longer life span, increased insulin sensitivity and stress resistance. In the new report, in yesterday’s online edition of Proceedings of the National Academy of Sciences, mice that were fed only every other day - but could gorge on the days they did eat - saw similar health benefits to ones that had their diet reduced by 40 percent. The cause of the health improvements from cutting back on diet is not fully understood, though many researchers had assumed that a long term reduction in calories was involved.

The new study by Mark Mattson and colleagues at the National Institute on Aging found equal benefits for mice that ate only every other day, but did not cut total calories because they ate twice as much on days they were not fasting. Mr Mattson said a study was in the planning stages to compare the health of a group of people fed three meals a day with a similar group eating the same diet and amount of food but consuming it within four hours and then fasting for 20 hours.

“Overeating is a big problem in the United States. It’s particularly troublesome that a lot of children are overweight. It’s still unclear the best way to get people to eat less...one possibility is skipping a meal a day,” Mr Mattson said. “Our study suggests that skipping meals is not bad for you.”

Carol Braunschweig of the University of Illinois at Chicago, who was not part of the study team, said she was intrigued by the suggestion that a drastic change in eating patterns might have benefits. “Identification of a beneficial eating pattern that could address some of the untoward effects of excess weight would be a very significant finding,” she said.

Mr Mattson said an earlier study found that mice that fasted every other day had extended lifespans and the new experiment found the mice also did better in factors involved in diabetes and nerve damage in the brain similar to Alzhemier’s disease. “We think what happens is going without food imposes a mild stress on cells and cells respond by increasing their ability to cope with more severe stress. It’s analogous to physical effects of exercise on muscle cells.” The researchers thought this stress happened throughout the body, and that might be the reason fasting seemed to increase lifespan and the animals became more resistant to the diseases of aging.

The dieting mice consumed 40% less food than mice eating normally and lost nearly half their body weight (49%) in the experiment, while the fasting mice weighed only a little less than mice eating normally.